The invention is directed to a soot blower for cleaning the interior surfaces of a boiler by discharging a suitable cleaning fluid from a nozzle against such surfaces. More particularly, the invention relates to a new and improved drive means for imparting horizontal and rotational motion to a lance tube mounting the fluid discharge nozzle.
Typically, in a soot blower of the long retracting or recovery type, a lance tube is moved through various long paths of travel horizontally forward into the heat exchange zone of a large public utility boiler or a pulp and paper mill recover boiler and thereafter retracted to its original starting position. During the traveling motion of the lance tube, the tube is rotated about its longitudinal axis and a cleaning fluid is discharged through a nozzle mounted at the forwardmost end of the tube so that the fluid may be directed against various internal surfaces of the boiler to remove undesirable soot accumulations. Accordingly, various means are required for imparting both linear and rotational movement to the lance tube during the traveling motion of a complete cleaning cycle. To advantage, the lance tube is rotatably supported by a traveling carriage which is, in turn, movably mounted within a housing channel arranged adjacent the public utility boiler.
The prior art has proposed many mechanical expedients, both automatic and manually operable, to drive the traveling carriage and to utilize a portion of the drive input for the traveling carriage as a rotary drive for rotating the lance tube. Such prior proposals have included chain or cable drives, rack-and-pinion arrangements and electric motors mounted on the traveling carriage. However, while the prior proposals have proven to be generally effective in achieving the intended purpose, they have been limited in providing efficient operation with maximum independent control for each of the horizontal and rotational movements of the lance tube.
It is a primary objective of the present invention to provide a novel drive system operable both as the horizontal drive for the traveling carriage and as a variable and reversible rotary drive for rotating the lance tube. In accordance with a significant feature of the invention, a variable, reversible rotational drive means, including, for example, either a hydrostatic drive, changeable gear train or both is mounted on the traveling carriage and includes a mechanical coupling with the lance tube whereby the output of the variable rotational drive means is utilized as the rotary drive to the lance tube. The horizontal drive for the traveling carriage is coupled to the rotary drive means so as to provide the necessary input drive for rotation of the lance tube. Accordingly, the rpm of the reversible, variable rotary drive means output may be selectively set within a predetermined range and the rotary direction of the drive output controlled at a pre-selected time during the working motion of the lance tube to provide a rotary motion whose components are controllable independently from the direction and magnitude of the horizontal drive. In this manner, the rotational speed and direction of the cleaning fluid discharged from the nozzle of the lance tube are precisely set to obtain the most effective cleaning action possible under the circumstances existing in a particular boiler while advantageously utilizing the horizontal carriage drive as the energy source for the rotary drive.
In accordance with a preferred embodiment for the rotary drive, a changeable gear train is mechanically coupled to the horizontal traveling carriage drive. The gear combinations of the gear train are selectively changeable to achieve a desired rotational velocity for the lance tube in view of the predetermined horizontal velocity of the traveling carriage. The rotary drive is controlled by means of a novel reversing mechanism whereby the direction of rotation of the lance tube may be pre-selected irrespective of the driving direction imparted to the rotary drive means during the advancing and retracting portions of the cleaning cycle by the horizontal drive means, as will appear.
Pursuant to another embodiment of the invention, maximum efficiency and control in the operation of the soot blower is achieved by utilizing a hydrostatic drive as the variable rotational drive means. The horizontal motion of the traveling carriage is used additionally as a source of input power for the hydrostatic drive. Inasmuch as the lance tube is necessarily moved along a horizontal path of travel to transport the cleaning fluid discharge nozzle through the full width of the boiler, a portion of the horizontal drive energy or the traveling momentum of the carriage may be selectively coupled to the hydrostatic drive input. Morover, the hydrostatic drive includes control means whereby the output direction of the drive is controllable and the velocity infinitely variable between predetermined limits.
To best advantage, the present invention provides a novel cable drive system operable to achieve a reliable, controllable horizontal motion for the traveling carriage. The cable drive system is coupled to the rotary drive of the lance tube by a suitable pulley rotatably mounted on the traveling carriage whereby the pulling action of the cable drive to impart horizontal motion to the traveling carriage tends to rotate the pulley thereby driving the rotary drive. Thus, a single power source is utilized to energize both the cable drive, and through the cable drive, the rotary drive for the lance tube. As discussed, the variable control feature of the rotary drive permits an independent control of the rotational velocity of the lance tube irrespective of the particular horizontal speed selected for the traveling carriage. The rotary drive may be operated to provide a desired rotational velocity with appropriate adjustments being made through the control means of the hydrostatic drive and/or by an appropriate adjustment to the changeable gear train to compensate for faster or slower horizontal speeds of the traveling carriage. The rotational direction of the lance tube is also selectively controlled so that a desired nozzle rotation is achieved in accordance with changes in the rotational direction of the input pulley.
For example, it has been found to be advantageous for effective cleaning to provide a unidirectional nozzle rotation during the entire cleaning cycle. However, utilization of the horizontal drive cables results in a change of input drive direction when the traveling carriage is retracted after the forward movement. Pursuant to the invention, the rotary direction of lance tube be maintained constant by in effect "reversing" the rotary drive to cancel out the effect of changing cable drive direction. Thus, the single power source may be used for maximum efficiency without any sacrifice in independent control for each of the horizontal velocity of the traveling carriage and the rotational velocity of the lance tube. In addition to the independent control for each of the components of cleaning fluid discharge nozzle motion, the novel cable drive and rotary drive apparatuses of the present invention each afford reliable, straightforward means for achieving lance tube motion during a cleaning cycle.
As another significant feature of the invention, the housing channel of the soot blower is formed to include a track-forming 90.degree. bend in each of the side walls of the channel. The traveling carriage is provided with rollers which are arranged and configured to engage the track-forming bends of the housing channel to support the traveling carriage for horizontal movements within the channel. The track-forming bends eliminate the need for additional structural components such as L-shaped bars to form the tracks and greatly reduce the cost and complexity in fabricating the housing channel. The track-forming bends may be formed in a simple bending operation during the time the housing channel is formed and there is no need to mount L-shaped bars to the housing channel after fabrication thereof. Thus, the track-forming bend feature of the invention provides an effective, yet inexpensive means for mounting the traveling carriage within the housing.
The present invention therefore provides several features which greatly enhance the ability of a soot blower to properly dislodge undesirable soot accumulations from the internal surfaces of large public utility boilers. The cable drive system affords a straightforward transverse drive for the traveling carriage while being ideally suited as an input for the variable rotary drive of the lance tube. The variable, reversible rotary drive in turn effectively utilizes the driving energy of the cable system while allowing independent control for the rotational velocity and direction of the lance tube.
For a better understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment of the invention and to the accompanying drawings.